The present invention relates to a system for, and a method of, controlling shifting in gear position in an automatic transmission, and more particularly to a system for, and a method of controlling shifting in gear position in an automatic transmission when an automotive vehicle which the automatic transmission is mounted on is subject to deceleration.
An automatic transmission of the E4N71B type is known. This automatic transmission is manufactured by Nissan Motor Company Limited in Japan and described in a publication "NISSAN AUTOMATIC TRANSMISSION L4N71B TYPE, E4N71B TYPE, SERVICE MANUAL 1982 (A261C04)" issued by Nissan Motor Company Limited on November in 1982. This known transmission comprises a downshift solenoid, a shift switch, an idle switch, a vehicle speed sensor, a brake switch, and a control unit. As described on page 12 of the above-mentioned publication, the downshift solenoid is rendered ON when the shift switch indicates that the third gear position is established in D range, the vehicle speed sensor detects a vehicle speed falling in a predetermined range from 30 km/h to 50 km/h, the brake switch is rendered ON, and the idle contacts of the throttle switch are rendered ON. According to this downshift control, the downshift solenoid is rendered OFF to cause an upshift to take place in the automatic transmission when the idle switch is rendered OFF in response to the driver' s depressing of an accelerator pedal. This abrupt upshift from the downshifted state induces a shock and an unplesant ride feel or sensation to the driver.
An object of the present invention, therefore, is to provide a system for, and a method of, controlling the gear position in an automatic transmission when an automotive vehicle which the automatic transmission is mounted on is subject to deceleration, which are improved such that the above-mentioned shock nor the neither unplesant ride feel encountered in the prior art are eliminated or alleviated.